Determination of IgG Subclasses and Avidity of Antithyroid Peroxidase Antibodies in Patients with Subclinical Hypothyroidism – A Comparison with Patients with Overt Hypothyroidism

• Published in: Hormone research Vol. 59; no. 3; pp. 118 - 124
• Main Authors: Silva, L.M., Chavez, J., Canalli, M.H.B., Zanetti, C.R.
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland S. Karger AG 01.01.2003
• Subjects: Adult; Aged; Antibodies, Blocking - immunology; Antibody Affinity - physiology; Enzyme-Linked Immunosorbent Assay; Female; Humans; Hypothyroidism - immunology; Immunoglobulin G - analysis; Immunoglobulin G - classification; Immunoglobulin G - immunology; Iodide Peroxidase - immunology; Middle Aged; Original Paper; Predictive Value of Tests; Thyroid Function Tests; Thyroiditis, Autoimmune - immunology; Thyrotropin - blood; Thyroxine - blood; Anti-TPO; Subclinical hypothyroidism; Anti-TPO avidity; Anti-TPO subclasses
• ISSN: 1663-2818; 0301-0163; 1663-2826
• DOI: 10.1159/000069069

Objective: To evaluate the immunoglobulin G subclasses of anti-TPO and antibody avidity in patients with subclinical hypothyroidism (sH), overt hypothyroidism (H) and a control group (C). Methods: According to the TSH, fT4 and anti-TPO antibody levels, appraised by immunometric assays, 95 female patients were divided into three groups (sH, H and C). IgG subclass levels and avidity were measured by a homemade ELISA. Results were analyzed by nonparametric tests and Spearman’s rank correlation. Results: The predominant IgG subclasses detected in both case groups were IgG1 and IgG4 with a significantly higher level of IgG4 in the sH group. Consequently, the IgG1/IgG4 ratio was significantly lower in sH patients. Conclusion: The higher levels of IgG4 anti-TPO reduced significantly the IgG1/IgG4 ratio in sH patients. These results permit to envisage that increasing this ratio could be useful as a positive predictive factor for the development of overt disease in such patients.